Network Function Virtualization (NFV) is expected to be a crucial enabler of Beyond 5G (B5G) networks, supporting new services with stringent requirements, while offering high flexibility and configurability. In this paper, we consider the joint problem of Virtual Network Function (VNF) placement alongside computational and communication resource allocation in a mobile network to minimize total power expenditure while satisfying the Service Function Chain (SFC), throughput and delay requirements. We explicitly account for the Access Network (AN) and formulate a general Mixed Integer Linear Program (MILP). Due to the high complexity of the latter, we propose an efficient heuristic, which is shown to significantly outperform the State-of-Art (SoA), while achieving up to 78% of the optimal energy efficiency with up to 742 times lower complexity.